The present invention relates generally to two-way or bidirectional cable television systems and, and more particularly to method and apparatus of ingress testing a two-way CATV system which provides for remote selection of nodes to be tested and remote viewing of ingress test measurements obtained from the selected node.
Community Antenna Television (xe2x80x9cCATVxe2x80x9d) systems are used in a widespread manner for the transmission and distribution of television signals to end users, or subscribers. In general, CATV systems comprise a headend facility and a distribution network. The headend facility obtains television signals associated with a plurality of CATV channels and generates a broadband CATV signal therefrom. The distribution network then delivers the CATV broadband signal to television receivers located within the residences and business establishments of subscribers.
Two-way CATV networks have been touted as a promising method of providing communications in cable television systems. Accordingly, two-way networks were widely specified in CATV service provider franchise agreements over the last twenty years. Technical problems, however, have inhibited wide deployment of such two-way networks. In particular, interference due to ingress signals has greatly affected the quality of return path communications in two-way networks. Return path communications are communications from the subscribers to the headend facility.
Ingress signals comprise noise signals that are generated by sources external to the CATV network and are radiated onto the CATV network through cable faults, terminations, and the like. Some sources of ingress include international short-wave broadcasts; citizens band and ham radio transmissions; television receivers; computers; neon signs, electrical motors, hair dryers, garbage disposals, and other household appliances, and it has been estimated that 95% of ingress signal power originates in subscribers"" homes.
Ingress signals are particularly troublesome in the context of return path communications because of the CATV two-way network architecture. In a CATV network, a large number of subscriber generated signals are funneled toward the headend. The ingress signal power on each of the subscriber generated signals is therefore combined and amplified, resulting in a relatively high ingress signal power at the headend facility.
Since consumer demand is currently high for various two-way services such as broadband internet access, interactive TV, and telephony, CATV franchises are interested in providing these services to their subscribers. However, in order to provide these services in a reliable manner, CATV franchises must eliminate or reduce ingress signals that interfere with two-way communications. In this regard, CATV franchises have implemented their CATV networks using more of a star topography with multiple nodes that each have a separate reverse path instead of the simpler tree topography. Each node of the CATV network, services only a portion of all of the subscribers instead of all the subscribers being serviced by a single node. The star topography inherently lowers the level of the ingress signal at the headend facility because each ingress signal includes a fewer number of ingress sources (e.g. subscribers). Furthermore, the star topography helps technicians determine the origination of the ingress signals because the technician may determine that ingress is originating in a certain node of the CATV network, thus eliminating subscribers of other nodes as the source of ingress. For example, in a 20,000 subscriber network where each node services 2,000 subscribers, if the technician can determine that ingress is concentrated in a single node of the network, then the technician may focus on the 2,000 subscribers serviced by that node, thereby eliminating 18,000 subscribers from consideration.
Even with a star topography, troubleshooting ingress can be a real challenge since ingress can be transient or constant, intermittent or predictably repetitive. Moreover, ingress signals may result from signal entry on one node or multiple points on one node, and may be broadband or narrow band in nature. Furthermore, ingress on one node may effect other nodes. Because of these characteristics, technicians must be able to make adjustments to a node of the CATV network and easily determine in the field whether the adjustments have remedied the problem. In particular, technicians need to be able determine in the field what effect the adjustments had on the upstream signals of the adjusted node, other nodes, and on the CATV system as a whole.
Reverse spectrum measurements of upstream signals as received by the headend facility are helpful in gaining insight into the ingress situation of the CATV network. However, as of yet there has been no automated way for a technician in the field to selectively obtain reverse spectrum measurements for different nodes of the CATV network. Accordingly, there is a need for a field client which may provide the technician in the field with reverse spectrum measurements of a certain node of the CATV network. Furthermore, there is a need for a headend facility that can receive a request to obtain reverse spectrum measurements for a node of the CATV network, obtain reverse spectrum measurements for the requested node, and provide the field client with the obtained reverse spectrum measurements.
The present invention fulfills the above needs, as well as others, by providing a CATV system which (i) allows a technician in the field to request via a field client that a node of the CATV system be tested for ingress, and (ii) allows the technician to view the results of the tested node. An exemplary method according to the present invention is a method of testing a CATV system having a headend facility that is coupled to a CATV distribution network that includes a plurality of nodes through which upstream signals are transmitted to the headend facility. One step of the method includes receiving at the headend facility a first reverse telemetry signal transmitted by a first field client that is coupled to the CATV distribution network at a first location. Another step of the method includes selecting at the headend facility a first test node from the plurality of nodes of the CATV distribution network, wherein the selection is based upon the received first reverse telemetry signal. The method also includes the step of measuring first upstream signals from the selected first test node to obtain a first plurality of measurement values for the first upstream signals. Finally, the method includes transmitting from the headend facility via the CATV distribution network a forward telemetry signal that includes the first plurality of measurement values.
The present invention further includes various apparatus for carrying out the above method. For example, one apparatus according to the present invention includes a CATV distribution network, a test point switch, an RF receiver, an RF transmitter, and a controller. The CATV distribution network includes a plurality of nodes through which upstream signals are transmitted. The test point switch is coupled to the plurality of nodes and is operable to electrically couple a first test node of the plurality of nodes to the RF receiver in response to a first control signal that is indicative of a first node identifier being applied to a node selection input of the test point switch. The first field client is coupled to the CATV distribution network at a first location, and is operable to transmit a first reverse telemetry signal that includes the first node identifier that identifies the first test node of the plurality of nodes.
The RF receiver is coupled to said test point switch and is operable to receive from said test point switch, a reverse RF signal that includes said first reverse telemetry signal. The RF receiver is also operable to measure first upstream signals received from the first test node to obtain a first plurality of measurement values for the first upstream signals. The RF transmitter is coupled to the CATV distribution network and is operable to transmit to the first field client via the CATV distribution network, a forward telemetry signal that includes the first plurality of measurement values for the first upstream signals. The controller is coupled to said RF receiver, said RF transmitter, and said test point switch. Moreover, the controller is operable to (i) control operation of the RF receiver and the RF transmitter, and (ii) cause the test point switch to electrically couple the first test node to the RF receiver by applying the first control signal to the node selection input.
The above features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings.